1971 Corvette 454 Engine Rebuild

[John G.]

Learned Yesterday The Rings On My 1971 Ls5 Engine Are Shot. Current Ncrs Member To Perform The Repairs. Want To Read And Learn About The Process And What The Ncrs Guidelines Are. Interested In Any Input Or Things To Watch For During The Restoration.

[Joe R.]

Re: 1971 Corvette 454 Engine Rebuild

Learned Yesterday The Rings On My 1971 Ls5 Engine Are Shot. Current Ncrs Member To Perform The Repairs. Want To Read And Learn About The Process And What The Ncrs Guidelines Are. Interested In Any Input Or Things To Watch For During The Restoration.

Hi John,

Just curious, how do you know the rings are a goner? Who are you planning to use for the repairs? What repairs are you planning to do? Are you restoring the engine? If so, are you going bone stock or would you like to gain a few ponies while retaining all the original components for flight judging?

Joe

[Clem Z.]

Re: 1971 Corvette 454 Engine Rebuild

a leak down test is the best way to determine the condition of the engine.

[John G.]

Re: 1971 Corvette 454 Engine Rebuild

Clem, thanks for your reply. Yes, the leak down test was performed on both sides of the engine.

[Michael W.]

Re: 1971 Corvette 454 Engine Rebuild

NCRS guidelines? If you mean Flight Judging, the engine should appear no different- no better, no worse, than the day it was delivered to the first owner. If you're going beyond that and contemplating a wild cam that may change the idle characteristics, this may affect a PV.

Above all do NOT allow the shop to 'deck the block' as this will remove the all-important broach marks and pad stampings. 99.9% of blocks do not require 'decking' or other extreme machining during routine overhaul.

BTW- please turn off the software that Puts A Capital Letter At The Beginning Of Every Word. It makes posts very hard to read.

[Thomas H.]

Re: 1971 Corvette 454 Engine Rebuild

When I rebuilt my 71 LS5 several years ago, I wanted to stay as close to factory specs as I could. Ended up using a Crane 969391 cam along with Speed pro ZH661 Hypereutectic pistons. Worked out real well.

As was stated before, do not let the machine shop deck the block or you'll lose the broach marks and the numbers on the pad.

Good luck

Tom

[Duke W.]

Re: 1971 Corvette 454 Engine Rebuild

What Joe asked...

1. Does it consume excess oil?

2. What are the leakdown test results that were used to determine that the engine is "shot"?

There's little the TDB can offer in the way of advice without seeing some test data.

If you do decide to proceed with a rebuild, the easiest thing to do is increase the compression to about 10:1 with suitable replacement pistons. Your engine was built with and advertised CR of 8.5:1 and was designed for regular unleaded gasoline. Modern premium will support 10:1 true, which will yield 6-8 percent more torque/power and increase fuel mileage by a similar amount.

If you want "more power", massage the heads, which is good for another 7-10 percent more top end power.

Use an exact OE replacement cam.

Basics of engine restoration have been covered pretty thoroughly here and in The Corvette Restorer including what you can do to improve performance without affecting visual or normal operating behavior that is critical to passing a PV.

You say a current NCRS member is doing the rebuild. How about getting him in on this discussion?

Duke

[Thomas H.]

Re: 1971 Corvette 454 Engine Rebuild

Use an exact OE replacement cam.

Duke

The cam I referenced in my post was, at the time, part of the Crane Muscle Car OE replacement cams. I don't believe one was available thru GM which is why I went with the Crane cam. As far as I could tell by comparing specs, it had the same profile and lift of the OE cam for a 365hp 454.

Tom

[Duke W.]

Re: 1971 Corvette 454 Engine Rebuild

I don't know about the Crane, but the Sealed Power CS1093M from Federal Mogul is built to the GM print.

Basic specs are 214/218 deg @ .050" duration, POMLs 110/120, 115 LSA, lobe lift .27143/.28235"

You can look up this number and specs at the NAPA Web site.

Duke

[Thomas H.]

Re: 1971 Corvette 454 Engine Rebuild

I don't know about the Crane, but the Sealed Power CS1093M from Federal Mogul is built to the GM print.

Basic specs are 214/218 deg @ .050" duration, POMLs 110/120, 115 LSA, lobe lift .27143/.28235"

You can look up this number and specs at the NAPA Web site.

Duke

Went through my notes fomr the engine build and found the cam card. Yup, same specs. Like I said, when I was doing this engine several years ago, I couldn't locate another source for one with a stock profile other then the Crane. Could be I just didn't look hard enough..........

Tom